1. Field of the Invention
The present invention relates to a status display system for storage device, e.g., at least one disk array device, which operates a plurality of physical devices in parallel as at least one logic device and is adapted to display a status of the logic device.
There is recently a tendency to demand, in a computer system, a transfer of large amounts of data at high speed, and therefore, auxiliary storage devices are also required to transfer large amounts of data at high speed to exchange data with a host device.
To meet this requirement, auxiliary storage device, e.g., magnetic disk array device, have been developed, which are mainly constituted from at least one logic device including a plurality of physical devices such as several units of disk drives and which enable plural bytes of data to be transferred in parallel between the host device and the logic device.
2. Description of the Related Art
Here, the conventional magnetic disk array device, which is representative of storage device, will be explained more specifically.
In general, in a single unit of a magnetic disk drive, data transfer speed is limited by a rotation speed of a motor which rotates a magnetic disk as a recording medium. Accordingly, if it is intended to attain high speed operation by increasing a data transfer speed, it is necessary to perform read/write operations in parallel by driving a plurality of disk drives, called disk array drives, simultaneously. At this time, according to a command from a host device, the spindle motors of the magnetic disk drives such as a disk array device connected in parallel with the host device, are synchronously rotated, so that it becomes possible to perform a parallel transfer of data.
Further, in addition to the data transfer at high speed, fault tolerance of the whole system is also required for such disk array device so that sufficient reliability for the large amounts of data can be ensured without decreasing the data transfer speed.
To attain such a fault tolerant system, even though a failure, such as the inability to read data from one disk drive of a plurality of disk drives, has occurred, it is necessary for the disk array device to be constructed so that the data of the failed disk drive can be reconstructed immediately without stopping operation of the whole system of disk array device.
Some kinds of disk array device in practical use, in which the above-mentioned data transfer at high speed and the fault tolerance can be satisfied simultaneously, have begun to be announced by various computer manufacturers as the products of disk array device called RAID (Redundant Arrays of Inexpensive Disks) 1 to RAID5.
Among these RAIDs1-5, RAID3, is especially adequate for the case where large amounts of data have to be processed continuously at high speed, e.g., scientific calculations, will be described in more detail.
In the RAID3, the disk array device typically includes a plurality of disk drives for data transfer (for example, eight (8) disk drives) and a disk drive for parity checking, all these disk drives operating in parallel simultaneously. In this case, some given parity data corresponding to the parallel data of the respective disk drives for data transfer are previously stored in the disk drive for parity checking (parity disk drive). In such a construction, even though one disk drive of a plurality of disk drives fails so that the data cannot be read out, the data can be reconstructed by reading the parity data from the parity disk drive.
Further, in the RAID3, a spare storage disk drive is also provided. All the data in the failed disk drive is automatically reconstructed and transferred into the spare storage disk drive. If the reconstruction process is completed, the spare storage device can be utilized as a normal disk drive, in cooperation with the other disk drives for data transfer.
In this manner, the disk array device as represented by the RAID3, which enables large amounts of data to be transferred at relatively high speed (for example, 36 MBytes/sec) and has substantially fault tolerant characteristics, can be prepared. Hereafter, the whole construction of such disk array device will be described with reference to FIG. 1, so that the disk array device can be understood more clearly.
FIG. 1 shows a schematic construction of a plurality of conventional disk array devices which are representative of storage device. In FIG. 1, the disk array devices are provided with logic devices 10-1 to 10-n, such as n groups of disk array devices and a disk controller 20 for controlling these logic devices 10-1, to 10-n in accordance with an instruction from a host device, e.g., a host computer.
Each of the aforementioned logic devices 10-1 to 10-n includes physical devices 11-0 to 11-8, such as nine units of disk drives, corresponding to respective bytes of eight bytes (8 bytes) of data and a parity byte, and a spare physical device 11-9, such as one spare storage disk drive.
The disk controller 20 of the disk array drives is further provided with ten device controllers 21-0 to 21-9 corresponding to the respective physical devices constituting the logic devices 10-1-10-n. The physical devices included in the respective logic devices 10-1 to 10-n are connected to the corresponding device controllers 21-0 to 21-9 through multiple lines.
Each of the device controllers 21-0 to 21-9 is constructed so as to select any one of the physical devices 11 connected thereto in accordance with a designated address, and to perform data transfer operation with the selected physical device.
The disk controller 20 is constructed so as to designate addresses to these device controllers 21-0 to 21-9 in accordance with an instruction from the host computer, and to instruct read/write operations to the physical devices. At this time, the disk controller 20 divides data transferred through a channel from the host computer and transfers the divided data to the respective device controllers 21-0 to 21-9. Further, the disk controller 20 combines data transferred from the respective physical devices 11 through the device controllers 21-0 to 21-9 into 8 bytes of parallel data and transfers the combined data to the channel in accordance with the aforementioned instruction.
Accordingly, when at least one disk array device as shown in FIG. 1 is utilized, it becomes possible for eight bytes of data to be transferred during the time it takes to transfer one byte of data utilizing only a single disk drive. Therefore, the time that is required to input or output data can be remarkably shortened.
However, as described above, the individual device controllers 21-0 to 21-9 select the physical devices 11 connected thereto in accordance with the designated addresses and control the selected devices 11 in the disk array devices. Accordingly, the status of the logic devices as a whole designated by the addresses cannot be obtained until status information from the respective physical devices is combined together through the ten device controllers 21-0 to 21-9. In such a construction, the disk controller 20 including the device controllers 21-0 to 21-9 administers all the status information of the respective logic devices 10-1-10-n, and whether or not the individual physical devices 11 are in a ready condition is displayed by turning on light emitting diodes (LED) or the like provided on housings in the logic devices 10.
Practically, the aforementioned display by means of the light emitting diodes or the like is an extremely simple one, merely indicating whether or not the respective disks are rotating after an electric power is supplied to the respective physical devices.
Therefore, there are some cases where the individual physical devices are in the ready condition, but each of the logic devices constituted thereby is not in an operable condition as an overall logic device, such as the case where start-up processing of the disk array devices has not been normally completed or the case where an initial micro program loading (IMPL) is being executed for the logical devices. However, in regard to the display by means of the light emitting diodes, the ready condition is indicated even in these cases. Accordingly, a problem occurs in that an operator (user) is likely to misunderstand that each logic device is in an operable condition, and is likely not to notice that the logic device is not in an operable condition until receiving error information notifying that the display is erroneous, which is issued in response to a write command or a read command from the host computer.
On the other hand, the contents of a status information table provided in the disk controller 20 are used for a control processing executed in the disk controller 20. Thus, the contents of the status information table cannot be referred to, unless a specialized command for executing a diagnostic program is input from the host computer. Moreover, since the diagnostic program is usually complicated, it takes much time to start up the diagnostic program. Consequently, another problem occurs in that the status information effective for a logic device cannot be offered to the operator accurately and rapidly.